CSS (Cascading Style Sheets) is a language for specifying how documents are presented to users, It is used to build web pages along with HTML. It has the advantage of adding features and properties to the structure of web pages, such as the colors, fonts, and styles that a web page takes.
and you can set the css with different way to get same result like :
body { color: red; }
h1 { color: #00ff00; }
p.ex { color: rgb(0,0,255); }
and we can use reset stylesheet is to reduce browser inconsistencies in things like default line heights, margins and font sizes of headings,Reset styles quite often appear in CSS frameworks.
Three Ways to Insert CSS External CSS (preferred) Internal CSS Inline CSS